Segment Information (Financial Information by Segment) (Details)		3 Months Ended				6 Months Ended
		Jun. 30, 2016 USD ($)		Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) reportable_segment		Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | reportable_segment						5
Revenues
Net earned premiums		$ 1,202,224,000			$ 2,138,258,000	$ 2,617,462,000		$ 4,297,820,000
Fees and other income		328,305,000			323,609,000	685,995,000		603,171,000
Net investment income		119,820,000			167,786,000	255,527,000		320,059,000
Net realized gains on investments		21,626,000			11,999,000	183,344,000	[1]	15,954,000
Amortization of deferred gain on disposal of businesses		125,818,000	[2]		3,242,000	173,414,000	[3]	6,500,000
Gain on pension plan curtailment		0		$ 29,578,000	0	29,578,000		0
Total revenues		1,797,793,000			2,644,894,000	3,945,320,000		5,243,504,000
Benefits, losses and expenses
Policyholder benefits		400,814,000			1,267,714,000	944,630,000		2,478,441,000
Amortization of deferred acquisition costs and value of business acquired		342,640,000			353,883,000	676,982,000		722,886,000
Underwriting, general and administrative expenses		803,595,000			969,494,000	1,720,954,000		1,891,403,000
Interest expense		15,232,000			13,778,000	29,735,000		27,556,000
Total benefits, losses and expenses		1,562,281,000			2,604,869,000	3,372,301,000		5,120,286,000
Segment income (loss) before provision (benefit) for income tax		235,512,000			40,025,000	573,019,000		123,218,000
Provision (benefit) for income taxes		66,163,000			7,236,000	183,352,000		40,385,000
Net income		169,349,000			32,789,000	389,667,000		82,833,000
Total assets		29,804,213,000				29,804,213,000			$ 30,036,402,000
Operating Segments | Solutions
Revenues
Net earned premiums		755,252,000			752,604,000	1,494,176,000		1,507,081,000
Fees and other income		202,908,000			178,578,000	441,017,000		351,646,000
Net investment income		88,362,000			99,976,000	177,285,000		192,167,000
Net realized gains on investments		0			0	0	[1]	0
Amortization of deferred gain on disposal of businesses		0	[2]		0	0	[3]	0
Gain on pension plan curtailment						0
Total revenues		1,046,522,000			1,031,158,000	2,112,478,000		2,050,894,000
Benefits, losses and expenses
Policyholder benefits		222,230,000			235,099,000	448,981,000		450,647,000
Amortization of deferred acquisition costs and value of business acquired		283,032,000			276,823,000	552,042,000		541,855,000
Underwriting, general and administrative expenses		475,935,000			437,917,000	977,145,000		897,201,000
Interest expense		0			0	0		0
Total benefits, losses and expenses		981,197,000			949,839,000	1,978,168,000		1,889,703,000
Segment income (loss) before provision (benefit) for income tax		65,325,000			81,319,000	134,310,000		161,191,000
Provision (benefit) for income taxes		3,925,000			20,504,000	25,776,000		46,017,000
Net income		61,400,000			60,815,000	108,534,000		115,174,000
Total assets		14,830,610,000				14,830,610,000			14,356,484,000
Operating Segments | Specialty Property
Revenues
Net earned premiums		451,318,000			532,022,000	920,927,000		1,060,468,000
Fees and other income		109,846,000			106,128,000	217,608,000		190,364,000
Net investment income		17,823,000			25,443,000	36,167,000		45,958,000
Net realized gains on investments		0			0	0	[1]	0
Amortization of deferred gain on disposal of businesses		0	[2]		0	0	[3]	0
Gain on pension plan curtailment						0
Total revenues		578,987,000			663,593,000	1,174,702,000		1,296,790,000
Benefits, losses and expenses
Policyholder benefits		202,659,000			214,605,000	382,131,000		419,208,000
Amortization of deferred acquisition costs and value of business acquired		59,608,000			66,111,000	119,082,000		158,180,000
Underwriting, general and administrative expenses		231,920,000			252,495,000	473,354,000		476,107,000
Interest expense		0			0	0		0
Total benefits, losses and expenses		494,187,000			533,211,000	974,567,000		1,053,495,000
Segment income (loss) before provision (benefit) for income tax		84,800,000			130,382,000	200,135,000		243,295,000
Provision (benefit) for income taxes		27,859,000			42,848,000	66,843,000		80,674,000
Net income		56,941,000			87,534,000	133,292,000		162,621,000
Total assets		3,632,142,000				3,632,142,000			3,648,738,000
Operating Segments | Health
Revenues
Net earned premiums		(4,346,000)			584,443,000	24,388,000		1,194,185,000
Fees and other income		8,284,000			17,047,000	13,402,000		33,023,000
Net investment income		1,983,000			7,014,000	5,921,000		14,021,000
Net realized gains on investments		0			0	0	[1]	0
Amortization of deferred gain on disposal of businesses		0	[2]		0	0	[3]	0
Gain on pension plan curtailment						0
Total revenues		5,921,000			608,504,000	43,711,000		1,241,229,000
Benefits, losses and expenses
Policyholder benefits		(24,075,000)			625,323,000	(4,963,000)		1,230,086,000
Amortization of deferred acquisition costs and value of business acquired		0			2,917,000	0		7,190,000
Underwriting, general and administrative expenses		37,763,000			158,608,000	90,718,000		287,786,000
Interest expense		0			0	0		0
Total benefits, losses and expenses		13,688,000			786,848,000	85,755,000		1,525,062,000
Segment income (loss) before provision (benefit) for income tax		(7,767,000)			(178,344,000)	(42,044,000)		(283,833,000)
Provision (benefit) for income taxes		(2,341,000)			(54,569,000)	(9,445,000)		(76,089,000)
Net income		(5,426,000)			(123,775,000)	(32,599,000)		(207,744,000)
Total assets		723,107,000				723,107,000			1,437,032,000
Operating Segments | Employee Benefits
Revenues
Net earned premiums					269,189,000	177,971,000	[4]	536,086,000
Fees and other income					6,460,000	4,244,000		12,734,000
Net investment income					30,020,000	17,340,000	[4]	57,841,000
Net realized gains on investments					0	0	[1],[4]	0
Amortization of deferred gain on disposal of businesses					0	0	[3],[4]	0
Gain on pension plan curtailment	[4]					0
Total revenues					305,669,000	199,555,000	[4]	606,661,000
Benefits, losses and expenses
Policyholder benefits					192,687,000	118,481,000	[4]	378,500,000
Amortization of deferred acquisition costs and value of business acquired					8,032,000	5,858,000	[4]	15,661,000
Underwriting, general and administrative expenses					88,241,000	58,469,000	[4]	179,580,000
Interest expense					0	0	[4]	0
Total benefits, losses and expenses					288,960,000	182,808,000	[4]	573,741,000
Segment income (loss) before provision (benefit) for income tax					16,709,000	16,747,000	[4]	32,920,000
Provision (benefit) for income taxes					5,441,000	6,277,000	[4]	11,504,000
Net income					11,268,000	10,470,000	[4]	21,416,000
Total assets		0				0			2,190,808,000
Operating Segments | Corporate & Other
Revenues
Net earned premiums		0			0	0		0
Fees and other income		7,267,000			15,396,000	9,724,000		15,404,000
Net investment income		11,652,000			5,333,000	18,814,000		10,072,000
Net realized gains on investments		21,626,000			11,999,000	183,344,000	[1]	15,954,000
Amortization of deferred gain on disposal of businesses		125,818,000	[2]		3,242,000	173,414,000	[3]	6,500,000
Gain on pension plan curtailment						29,578,000
Total revenues		166,363,000			35,970,000	414,874,000		47,930,000
Benefits, losses and expenses
Policyholder benefits		0			0	0		0
Amortization of deferred acquisition costs and value of business acquired		0			0	0		0
Underwriting, general and administrative expenses		57,977,000	[5]		32,233,000	121,268,000		50,729,000
Interest expense		15,232,000			13,778,000	29,735,000		27,556,000
Total benefits, losses and expenses		73,209,000			46,011,000	151,003,000		78,285,000
Segment income (loss) before provision (benefit) for income tax		93,154,000			(10,041,000)	263,871,000		(30,355,000)
Provision (benefit) for income taxes		36,720,000			(6,988,000)	93,901,000		(21,721,000)
Net income		56,434,000			$ (3,053,000)	169,970,000		$ (8,634,000)
Total assets		10,618,354,000				$ 10,618,354,000			$ 8,403,340,000
Trade Names | Operating Segments | Corporate & Other
Segment Reporting Information [Line Items]
Intangible asset impairment		$ 16,672,000

[1] Includes $146,727 related to assets transferred to Sun Life as part of the Assurant Employee Benefits sale on March 1, 2016.

[2] Includes $122,835 related to the additional deferred gain related to the Assurant Employee Benefits sale on March 1, 2016.

[3] Includes $167,428 related to the additional deferred gain related to the Assurant Employee Benefits sale on March 1, 2016.

[4] Assurant Employee Benefits amounts represent January and February results of operations prior to the sale on March 1, 2016.

[5] Corporate & Other includes a $16,672 intangible asset impairment charge related to trade names that will no longer be used or defended by the Company.